Gregan was left stranded in Yorkshire after failing to renew his passport.
Leeds had hoped the 32-year-old's application would be processed in time for him to join up in Norway later this week, but a current backlog is likely to prevent him from receiving his new passport before Leeds' second and final tour match against FK Ulf Sandnes on Monday.
Foxe will now have a great opportunity to take another step towards securing a permanent contract at Elland Road.
Gregan will now instead lead a reserve side in Saturday's friendly at Scarborough.